The present invention relates to a processing tool for employment by precision firearm marksmen in preparing cartridges having high inherent accuracy characteristics, and is comprised of a micro-adjustable case neck turning tool which enables one to consistently achieve a measured close tolerance undersize trimming and trueing of a case neck outer diameter for minimal possibility of there being a mis-aligned angle of incidence in a loaded cartridge bullet-to-bore relationship upon cartridge ignition and discharge delivery of a bullet from the case mouth into the firearm barrel.
Part of the ballistic mechanics of safe discharge of a bullet from a cartridge case neck into the barrel bore upon cartridge ignition and firing is that there be a case neck expansion clearance space between the loaded cartridge case neck outer diameter and the firearm chamber neck recess inner diameter to allow for equalization of ignition pressures, and the recommended safe clearance standard in the foregoing respect is typically 0.009-inch, which is based on an overclearance allowance for accumulated chamber fouling from powder and metal residue build up over repeated cartridge discharges between bore and chamber cleaning. However, with a 0.009-inch clearance there is also a sufficient room to allow for an angular mis-alignment of a seated cartridge within the chamber so that upon cartridge ignition the bullet enters the barrel at a cant rather than being on axial alignment with the bore, which results in a significant inaccuracy consequence when one is involved in the art of precision shooting.
It is typical of precision shooters, as a procedural technique of the art, to clean their firearm bore and chamber much more frequently than is either the custom or habit of other types of shooters. Therefore, chamber to cartridge oversize allowance for purposes of accommodating fouling accumulation with respect to ballistic safety and cartridge ignition pressure build up is reduced, and closer cartridge neck-to-chamber tolerances may be safely accommodated, typically on the order of 0.0015 to 0.002-inch with resultant reduction of the likelihood of bullet cant and axial mis-alignment thereof with the barrel bore axis upon cartridge ignition.
In addition to applicant's tool, the case neck turning tool most widely available for trimming case necks to close tolerance undersize for precision shooting is known as the Marquart Precision Case Neck Turning Tool, manufactured by the Marquart Precision Company, Inc., of Prescott, Ariz., which is adequate and effective for case neck trimming but is limited to a conventional threaded screw trimming blade displacement adjustment means and thereby lacking the precise trimming blade displacement and set capability provided by the tool of instant invention.
The applicant herein by his invention provides a novel and utilitarian tool for accomplishing reliable and accurately changed micro-adjustably measured cartridge case neck trimming blade vertical displacements and sets of 0.0002-inch with interpolated increments of 0.0001-inch in the procedural carrying out of case neck turning.